In a conventional air conditioner for a vehicle, generally, an air conditioning unit for adjusting air to be blown off into a vehicle compartment is surrounded by an air conditioning case and is mounted to a dash panel for separating the vehicle compartment from the engine room of the vehicle. Hence, there are cases where vibrations caused by the engine and a functional member for air conditioning such as an evaporator are transmitted to the air conditioning case via the dash panel to vibrate the side walls of the air conditioning case to thereby make noises.
JP patent No. 2004-196125A (corresponding to US 2004/0129010A) is known as a document to disclose the technology of reducing noises due to the vibrations of the air conditioning case. JP patent No. 2004-196125A discloses that the rigidity of the air conditioning case itself is increased to reduce the vibration of the air conditioning case by the use of the technology of integrally forming reinforcing ribs in the shape of a ladder or a lattice on the whole side wall of the air conditioning case, the technology of putting a weight formed separately on the air conditioning case, and the technology of changing the thickness of the air conditioning case for the respective portions of the case.
However, the above-mentioned conventional air conditioner for a vehicle can produce a measure of effect in inhibiting the occurrence of noises by reducing the vibration of surface of the air conditioning case but cannot produce a sufficient effect.
In an air conditioning unit shown in FIG. 9, an air conditioning case 100 is provided to accommodate an evaporator and a heater core, and an arm portion 101 is formed integrally with an outer wall of the air conditioning case 100 on the side of the engine room of the vehicle. A heater pipe base 103 for mounting a heater pipe 102 extending from the heater core is provided at a tip end portion of the arm portion 101 to be separate from the air conditioning case 100. Furthermore, a reinforcement rib 104 and a reinforcement plate 105 are provided at a base end side of the arm portion 101 so as to reinforce the part between the outer wall of the air conditioning case 100 and the arm portion 101. When the load is applied to the heater pipe 102, the load is transmitted to the air conditioning case 100 through the arm portion 101. In this case, the reinforcement rib 104 and the reinforcement plate 105 are used only for reinforcing the arm portion 101, but are not for reducing the noise due to vibration of the air conditioning case 100. Therefore, the reinforcement plate 105 is provided in a small range capable of reinforcing the arm portion 101, but is not extended to a large range.